The long term objective of this program is to develop a 12 VDC external drive system for the Jarvik-7 blood pump that is small and light weight enough to be worn in a side mounted vest arrangement making it completely portable. The proposed system will replace the currently used pnuematic system which weighs approximately 375 pounds. The new fully developed system, which will be hydraulic and powered by batteries, will occupy approximately 75 cubic inches (in two pieces) and weigh less than five pounds. The much discussed "quality of life" of the artificial heart recipient will be greatly improved by such a device. The Phase I effort will prove (in vitro) the feasibility of driving the implanted Jarvik-7 with an external hydraulic pump, and will make the first reduction in size of the electronic controller unit. The Phase II effort will complete the miniaturization of the electronic controller and will demonstrate the external drive system's capabilities through in vivo animal testing. The Office of Technology Assessment estimated that 84,000 persons per year are candidates for artificial hearts. The proposed program has the potential for improving the artificial heart's system weight, portability and reliability to make the device more "acceptable" to such thousands of potential users.